Field of the Invention
The present invention relates to testing devices and particularly to the testing of electrical currents used in magnetic non-destructive inspection. Even more particularly, the present invention relates to a method and apparatus for testing of electrical current by placing a toroidal probe around the current carrying member and determining the peak value of a pulse of current flowing therethrough.
In the field of non-destructive testing, there are devices utilized for the testing of materials using a magnetic inspection. As an example, drill pipe and other oil field tubulars are tested by magnetic inspection by methods which are known in the art and are thoroughly described in non-destructive testing literature. In short, magnetic inspection is a method for locating surface and sub-surface defects in ferro-magnetic materials such as for example steel. The material to be inspected is magnetized and defects (in the material being tested) produce magnetic "leakage" fields which fields can be detected by various means and are indicative of defects in the material.
The effectiveness of magnetic inspection is highly dependent upon obtaining the proper degree of magnetization in the object (such as for example a length of drill pipe) to be inspected. The magnetization is commonly obtained by subjecting the material under test to a magnetic field created by an electrical current. The strength of this field is directly proportional to the magnitude of the current. Therefore, by measuring the magnitude of the current the degree of magnetization is known.
in practice, large values of current are required to generate sufficient magnetization (several hundred to several thousand amperes). Generating continuous current of this magnitude would require extremely expensive and cumbersome equipment. Therefore, the art has developed lighter and less expensive equipment which can generate pulses of current of short duration (on the order of one second or less) while achieving the desired magnitude. The residual magnetic field left in the material as a result of the current pulse can be sufficient to perform the magnetic inspection provided that the current pulse is large enough. The strength of the residual field is dependent upon the magnitude of the current pulse. Specifications are known in the art which require minimum peak current values for a given size, shape, weight, composition, etc. for material being tested.
It is important to know the peak value of the current pulse so that one can know what adequate magnetization has occurred.
It is to this problem that the present invention is directed. The present invention provides a method and apparatus which measures the peak value of the current pulse and also contains a programmable alarm and reset feature which facilitates its use in a commercial inspection operation.
Thus, the present invention is not directly involved in the testing process itself of the ferro-magnetic material such as the length of drill pipe, but rather is involved in the testing of the electrical current being used to magnetize the drill pipe or like ferro-magnetic material being tested.
It is an object of the present invention to provide a current pulse monitor having the ability to measure current pulses of high magnitude and short duration.
It is another object of the present invention to provide a current pulse monitor having the ability to measure currents without the need to connect directly to the system to be tested and with essentially zero insertion loss.
Another object of the present invention is to provide a current pulse monitor having the ability to compare measured values automatically to any desired value set by the user.
Another object of the present invention is to provide a current pulse monitor having an alarm system which responds to the attainment of an amperage value over any desired value set by the user.
Another object of the present invention is to provide a current pulse monitor having an automatic reset capability which facilitates the use of the device in a commercial operation.
It is another object of the present invention to provide a current pulse monitor which is easy to use, portable, and easily adaptable to existing testing systems.